Liquid crystalline isonitriles

ABSTRACT

and R is straight-chain alkyl, straight-chain alkoxy, straight-chain alkanoyloxy or alkyloxycarbonyloxy, as well as compositions and electro-optical apparatuses containing them, are described.   WHEREIN X is   Liquid crystal substances or compounds of the formula

finite States oller et al.

atent 1 Dec. 9, 1975 LIQUID CRYSTALLINE ISONITRILES Inventors: Arthur Boller, Binningen; I-Ianspeter Scherrer, Therwil, both of Switzerland Hoffmann-La Roche Inc., Nutley, NJ.

Filed: Feb. 22, 1974 Appl. No.: 444,923

Assignee:

Foreign Application Priority Data Mar. 2, 1973 Switzerland 3099/73 US. Cl. 260/463; 252/299; 260/454; 260/465 D; 260/465 E; 260/471 R; 260/473 R; 350/150; 350/160 LC Int. Cl. .I. C07C 119/02 Field of Search 260/465 D, 334, 291, 463

References Cited UNITED STATES PATENTS 2/1974 Ratagiri et al. 350/160 X 3/1974 Boller et alv 260/465 X OTHER PUBLICATIONS Castellano et al.; J. Org. Chem., Vol. 33, No. 9, (1968).

Primary ExaminerLewis Gotts Assistant Examiner-Dolph H. Torrence Attorney, Agent, or FirmSamuel L. Welt; Bernard S. Leon; William G. lsgro [57] ABSTRACT Liquid crystal substances or compounds of the formula wherein X is and R is straight-chain alkyl, straight-chain alkoxy, straight-chain alkanoyloxy or alkyloxycarbonyloxy, as well as compositions and electro-optical apparatuses containing them, are described.

20 Claims, N0 Drawings LIQUID CRYSTALLINE ISONITRILES BRIEF SUMMARY OF THE INVENTION The invention relates to liquid crystalline compounds of the formula wherein X is DETAILED DESCRIPTION OF THE INVENTION The invention relates to compounds of the formula and R is straight-chain alkyl, straight-chain alkoxy, straight-chain alkanoyloxy or -alkyloxycarbonyloxy, or stated'another way, the invention relates to compounds of the formulas and ll R o-c NC Ib wherein R is as described above.

As used herein, the term straight-chain alkyl preferably denotes a straight-chain saturated hydrocarbon containing 1-7 carbon atoms, for example, methyl, ethyl, n-propyl, n-butyl, n-pentyl, and the like. The term straight-chain alkoxy preferably denotes a straight-chain alkyl ether group in which the alkyl group is as described above, for example, methoxy, ethoxy, n-propoxy, n-pentoxy, and the like. The term straight-chain alkanoyloxy preferably denotes a group derived from an aliphatic carboxylic acid of l-7 carbon atoms, for example, formyloxy, acetoxy, n-propionyloxy, and the like. The term alkyloxycarbonyloxy preferably denotes a carbonyloxy group wherein alkyl is a straight-chain alkyl as described above.

The compounds of formula I wherein X is are preferred. Especially preferred are the compounds of formula I wherein R is a straight-chain alkyl.

The compounds of formula I of the invention have, in the liquid crystalline state, a positive anisotropy of the dielectric constants (e 6 whereby a is the dielectric constant along the longitudinal axis of the molecule and e is the dielectric constant perpendicular thereto).

In an electric field the nematic liquid crystals of the invention orientate themselves (because 6 e y with the direction of their largest dielectric constant, that is, with their longitudinal axes, parallel to the field direction. This effect is utilized, inter alia, in the interaction between embedded molecules and the liquid crystalline molecules (guest-host interaction) described by J. H. I-leilmeier and L. A. Zanoni [Applied Physics Letters 13, 91 (1968)]. A further interesting application of the dielectric field orientation is present in the rotation cell discovered by M. Schadt and W. Helfrich [Applied Physics Letters 18, 127 (1971)], as well as in the Kerr cell described in Molecular-Crystals and Liquid Crystals 17, 355 (1972).

The electro-optical rotation cell of Schadt et al., supra, comprises essentially a condenser having transparent electrodes whose dielectric is formed from a nematic substance or liquid crystals having a dielectric constant of e e y The longitudinal axes of the molecules of the liquid crystal are arranged in twisted form between the condenser plates in the fieldless state, the twisting structure being defined by the given wall orientation of the molecules. After the application of an electrical potential to the condenser plates, the molecules adjust themselves with their longitudinal axes in the field direction (i.e., perpendicular to the surface of the plates), whereby linear polarized light is no longer rotated in the dielectric (the liquid crystal is uniaxially perpendicular to the surface of the plates). This effect is reversible and can be used for electrically controlling the optical transmissivity of the condenser.

In such light rotation cells it is very desirable to utilize compounds as dielectrics which possess a low melting point and slight viscosity. The compounds previ ously used for this purpose, e.g., p-[(p-ethyloxybenzylidene)amino]-benzonitrile have the disadvantage of first showing nematic properties at relatively high temperatures so that electro-optical apparatuses provided with such liquid crystals have to be heated and possible thermostatted. Further, said compounds possess a high viscosity which, for example, leads to considerable disadvantages in electro-optical apparatuses in that operation thereof requires relatively large voltages and long response times. Unexpectedly, it has now been discovered that the compounds of formula I of the invention possess liquid crystalline properties which correspond to the foregoing requirements. They exhibit not only the necessary large or strong positive anisotropy of the dielectric constants but also, individually or in the form of their mixtures with one another or with other nematic or non-nematic substances, they are liquid crystalline and exhibit slight viscosity at relatively low temperatures.

An advantage of the compounds of formula I over compounds formerly used for this purpose is their substantially greater stability in view of which they can be handled more conveniently.

The compounds of formula I can be prepared according to the processes hereinafter described. Specifically, y

a. dehydrating a compound of the formula i ii CO- or OC and R is straight-chain alkyl, straight-chain alkoxy,

straight-chain alkanoyloxy or alkyloxy-carbonyloxy, or

b. treating a compound of the formula wherein X and R are as hereinbefore described, with chloroform and a strong base, or

c. treating a compound of the formula wherein X and R are as previously described and Hal is fluorine, chlorine, bromine or iodine, with silver cyanide or copper cyanide and, subsequently, with potassium cyanide d. reducing a compound of the formula X N=C=Y wherein X and R are as hereinbefore described and Y is oxygen or sulfur, or

e. to prepare a compound of formula I wherein X is that is, a compound of the formula wherein R is as hereinbefore described, reacting a compound of the formula wherein R is as previously described, and Z isa leaving group, with p-hydroxybenzoisonitrile, or

f. to prepare a compound of formula I wherein X is that is, a compound of the formula wherein R is as previously described, reacting a compound of the formula CN coz' wherein Z is a leaving group, with a compound of the formula VII VIII

above, are:

p-n-butylbenzoic acid p-isocyanophenyl ester; p-n-pentylbenzoic acid p-isocyanophenyl ester; 1

p-n-hexylbenzoic acid p'-isocyanophenyl ester; p-n-heptylbenzoic acid p'-isocyanophenyl ester; p-n-octylbenzoic acid p-isocyanophenyl ester; I p-n-butyloxybenzoic acid p'-isocyanophenyl ester; p-n-pentyloxybenzoic acid p-isocyanophenyl ester; p-n-hexloxybenzoic acid p'-isocyanophenyl ester; p-n-heptyloxybenzoic acid p-isocyanophenyl ester; p-n-octyloxybenzoic acid p-isocyanophenyl ester;

6 p-methylcarbonyloxybenzoic acid p'-isocyanophenyl p-isocyanophenyl-p'-n-heptyloxycarbonyloxyphenyl ester; ester; and p-ethylcarbonyloxybenzoic acid p-isocyanophenyl p-isocyanophenyl-p'-n-octyloxycarbonyloxyphenyl ester; ester. p-n-propylcarbonyloxybenzoic acid p-isocyanophe- 5 nyl ester; In process embodiment (a) of the invention, a comp-n-butylcarbonyloxybenzoic acid p'-isocyanophenyl pound of formula II is dehydrated Conveniently, the

ester; dehydration is effected by utilizing an arylsulfonyl chlo- 1 p-n-pentylcarbonyloxybenzoic acid p'-isocyanopheride in pyridine or quinoline, or by utilizing phosphorus nyl ester; 10 oxychloride in combination with pyridine and potasp-n-hexylcarbonyloxybenzoic acid p'-isocyanophesium t-butylate. Especially preferred as the dehydrating nyl ester; agent, however, is phosgene in the presence of a terp-n-heptylcarbonyloxybenzoic acid p-isocyanophetiary amine such as, for example, trimethylamine, trinyl ester; ethylamine, tri-n-butylamine, N-methylmorpholine, p-n-octylcarbonyloxybenzoic acid p'-isocyanophenyl N,N-diethylaniline, pyridine, quinoline, or the like. The ester; reaction temperature advantageously is in the range of p-methyloxycarbonyloxybenzoic acid pfrom about 0 to about 150C., preferably in the range isocyanophenyl ester; of from about 10 to about 50C. The pressure at which p-ethyloxycarbonyloxybenzoic acid p'-isocyanophethe reaction mixture is carried out is not critical. If denyl ester; sired, the process can also be carried out at low temperp-n-propyloxycarbonyloxybenzoic acid p'- atures, that is, at temperatures in the range of from isocyanophenyl ester; about 50 to about 35C., using thionyl chloride in p-n-butyloxycarbonyloxybenzoic acid pthe presence of dimethylformamide.

isocyanophenyl ester; In process embodiment (b) of the invention, a comp-n-pentyloxycarbonyloxybenzoic acid ppound of formula III is treated with chloroform and a isocyanophenyl ester; strong base. Suitable strong bases are, for example, pop-n-hexyloxycarbonyloxybenzoic acid ptassium t-butylate or a solid alkali metal hydroxide, isocyanophenyl ester; such as, for example, sodium or potassium hydroxide. p-n-heptyloxycarbonyloxybenzoic acid p- The reaction is advantageously carried out in an inert isocyanophenyl ester; organic solvent such as benzene or toluene. The reacp-n-octyloxycarbonyloxybenzoic acid p'- tion temperature advantageously is in the range of from isocyanophenyl ester; about 0 to about 150C., preferably in the range of p-isocyanobenzoic acid p'-n-buty1phenyl ester; from about 50 to about 1 10C. The pressure at which p-isocyanobenzoic acid p'-n-pentylphenyl ester; the reaction is carried out is not critical. p-isocyanobenzoic acid p-n-hexylphenyl ester; In process embodiment (c) of the invention, a comp-isocyanobenzoic acid p-n-heptylphenyl ester; pound of formula IV forms a complex with silver or p-isocyanobenzoic acid p'-n-octylphenyl ester; copper cyanide, which when treated with potassium cyp-isocyanobenzoic acid p'-n-butyloxyphenyl ester; anide, is converted to a corresponding isonitrile of forp-isocyanobenzoic acid p-n-pentyloxyphenyl ester; mula I. Conveniently, the reaction can be carried out p-isocyanobenzoic acid p'-n-hexyloxyphenyl ester; 40 without a solvent or in an inert organic solvent, for exp-isocyanobenzoic acid p-n-heptyloxyphenyl ester; ample, an ether such as diethyl ether or tetrahydrofup-isocyanobenzoic acid p'-n-octyloxyphenyl ester; ran, dimethylformamide, benzene, toluene, cyclohexp-isocyanophenyl-p-n-ethylcarbonyloxyphenyl esane or acetonitrile. The reaction is carried out at a temter; perature below 180C, preferably at a temperature in p-isocyanophenyl-p-n-propylcarbonyloxyphenyl esthe range of from about 80 to about 150C. The prester; sure at which the reaction is carried out is not critical. p-isocyanophenyl-p'-n-butylcarbonyloxyphenyl es- In process embodiment (d) of the invention, a comter; pound of formula V is reduced. The reaction can be p-isocyanophenyl-p-n-pentylcarbonyloxyphenyl escarried out without a solvent or in an inert organic solvent, for example, an ether such as diethyl ether or tetp-isocyanophenyl-p-n-hexylcarbonyloxyphenyl esrahydrofuran, dimethylformamide, benzene, toluene,- cyclohexane, carbon tetrachloride, petroleum ether or p-isocyanophenyl-p-n-heptylcarbonyloxyphenyl esligroin. The reduction of an isocyanate of formula V is advantageously effected by heating in the presence of p-isocyanophenyl-p-n-octylcarbonyloxyphenyl estriethyl phosphite, triphenyltin hydride or cyclic phosphorus (III) amides, or by irradiation. The reduction of p-isocyanophenyl-p'-n-ethyloxycarbonyloxyphenyl an isothiocyanate of formula V is advantageously efester; fected with triethyl phosphine, triethyl phosphite, copp-isocyanophenyl-p'-n-propyloxycarbonyloxyphenyl per or triphenyltin hydride, or photolytically. The reacester; tion temperature, as required, advantageously lies in p-isocyanophenyl-p'-n-butyloxycarbonyloxyphenyl the range of from about 0 to about 180C, preferably ester; in the range of from about to about C. The p-isocyanophenyl-p'-n-pentyloxycarbonyloxypheny] pressure at which the reaction is carried out is not critiester; cal.

p-isocyanophenyl-p-n-hexyloxycarbonyloxyphenyl 65 In process embodiments (e) and (f) of the invention, ester; a compound of formula VI or a compound of formula VII is esterified. The esterification is conveniently carried out in an inert organic solvent, for example, an ether such as diethyl ether or tetrahydrofuran, dimethylformamide, benzene, toluene, cyclohexane or carbon tetrachloride.

In the compounds of formulas VI and VII, Z and Z, respectively, are preferably halogen, especially chlorine. In order to bind the hydrogen halide liberated in the reaction, an acid binding agent is conveniently utilized. Suitable acid binding agents are tertiary amines such as pyridines, and the like. The acid binding agent conveniently is utilized in a large excess, so that it can simultaneously serve as a solvent as well as an acid binding agent. The temperature and pressure at which the esterification is carried out are not critical and, in general, atmospheric pressure and temperatures in the range of from about room temperature to about the boiling temperature of the reaction mixture are utilized.

Exemplary of the physical properties of the nematic substances of formula I of the invention are the followp-n-hexyloxycarbonyloxybenzoic acid p'-isocyanophenyl ester p-isocyanobenzoic acid p'-n-hexylphenyl ester 50 58 pisocyanobenzoic acid p'-n-octylphenylester 43,5 63,5 p-isocyanobenzoic acid p'-n-hexyloxyphenylester 85.5 895 p-isocyanobenzoic acid p'-n-heptylcarbonyloxyphenylester 74 99.5

p-isocyanobenzoic acid p '-n-h exyloxycarbonyloxyphenylester 82.583.5 95

"monotrope "melting point clearin g point The compounds of formula I can be used in the form of mixtures with one another or with other nematic or non-nematic substances. Binary or ternary mixtures can be formed. Especially preferred mixtures comprise those whose composition corresponds to a eutectic.

Thus, in addition to mixtures with one another, the compounds of formula I of the invention can be utilized with other nematic or non-nematic substances, for example, with Schiffs bases of the formula R =N CN wherein R is straight-chain alkyl of 2 to 8 carbon atoms, straight-chain alkoxy of 4 to 7 carbon atoms or straight-chain alkanoyloxy of 2 to 8 carbon atoms.

The com pounds of formula I of the invention can also be used in the form of mixtures with compounds of the formula wherein R is straight-chain alkyl of 4 to 7 carbon atoms, or with compounds of the formula wherein R is straight-chain alkyl of 4 to 8 carbon atoms or straight-chain alkoxy of 5 to 8 carbon atoms. The starting materials of formulas Ill and IV, wherein X is utilized in process embodiments (b) and (c) can be prepared as described hereinafter.

A compound of the formula R COZ wherein R is as previously described, is reacted with a compound of the formula utilizing known reaction conditions to yield a compound of the formula known reaction conditions to yield the starting material of formulas III, wherein X is O H C i.e., a compound of the formula i.e., a compound of the formula I R C-() Hal IVa.

wherein R is as previously described.

The starting materials of formulas III and IV, wherein 3O Xis utilized in process embodiments (b) and (c) can be prepared as described hereinafter.

A compound of the formula utilizing known reaction conditions to yield a compound of the formula wherein R is as previously described.

The compound of formula is reduced utilizing known reaction conditions to yield the starting material of formula III, wherein X is i.e., a compound of the formula wherein R is as previously described.

The latter, as required, can be converted utilizing the known Sandmeyer reaction to the starting material of formula IV, wherein X is i.e., a compound of the formula wherein R is as previously described.

The starting materials of formulas (a), (b), (d) and (e) are known compounds or can be prepared according to known procedures.

The starting materials of formula II used in process embodiment (a) can be prepared by the reaction of compounds of formula III with formic acid ethyl ester, with formic acid in benzene witih subsequent azeotropic distillation of water, or with a mixture of acetic anhydride/formic acid.

The starting materials of formula V in which Y is oxygen, used in process embodiment (d), can be prepared by the reaction of the corresponding compound of formula III with phosgene. The compounds of formula V in which Y is sulfur, can be prepared by the reaction of the corresponding compound of formula III with thiophosgene or with carbon disulfide and a base via the corresponding diethiocarbamate.

The invention is further illustrated by the following Examples. All temperatures are given in degrees Centigrade, unless otherwise specified.

EXAMPLE 1 Preparation of p-n-hexylbenzoic acid p-isocyanophenyl ester 3.25 G. of p-n-hexylbenzoic acid p'-formamidophenyl ester were dissolved in 50 ml. of methylene chloride and 20 ml. of triethylamine and, at room temperature, treated dropwise with a solution of 1.4 g. of phosgene in 20 ml. of methylene chloride. Subsequently, the mixture was stirred for an additional hour, water was added thereto and then the organic phase was extracted twice with dilute hydrochloric acid. The crude product obtained after being washed neutral, dried and concentrated was chromatographed on 300 g. of silica gel with benzene/ 1% acetone, whereby there were obtained 1.6 g. of p-n-hexylbenzoic acid p-isocyanophenyl ester which crystallized in a refrigerator. Crystals having a melting point of 2626.5 and a clearing point of 41 .5 precipitate from hexane at about 20.

The starting material p-n-hexylbenzoic acid p-formamidophenyl ester was prepared as follows:

9.2 G. of N-benzylidene p-aminophenol was treated in 70 ml. of absolute pyridine at 5 with 10.4 g. of p-nhexylbenzoic acid chloride in 25 ml. of pyridine. The mixture was stirred overnight at room temperature and then poured with stirring onto ice-water. The precipitated product was removed by filtration, washed thoroughly with water, taken up in methylene chloride, dried and concentrated. After recrystallization, there was obtained 12.6 g. of ester having a melting point of ll.5l03.5 and a clearing point of 114.

To cleave the Schiffs base, the ester was dissolved in ether. Upon shaking with dilute hydrochloric acid, the hydrochloride salt of the amine precipitated, which was then removed by filtration and washed thoroughly with ether. The hydrochloride salt was decomposed with saturated soda solution and the mixture extracted with ether, whereby there was obtained 9.2 g. of practically pure p-n-hexyibenzoic acid p-aminophenyl ester. After boiling with formic acid ethyl ester for 24 hours, there was obtained in almost quantitative yield p-n-hexylbenzoic acid p'-formarnidophenyl ester which, after recrystallization from ethyl acetate, had a melting point of 126.5".

in a manner similar to that described above, the following compounds were prepared:

p-n-butylbenzoic acid p'-isocyanophenyl ester having a melting point of 505 and a clearing point of 355 (monotrope);

p-n-pentylbenzoic acid p'-isocyanophenyl ester having a melting point of 525 and a clearing point of 505 (monotrope);

p-n-heptyibenzcic acid p-isocyanophenyl ester having a melting point of 37.538 and a clearing point of 50.5-5 1; pn-octylbenzoic acid p-isocyanophenyl ester having a melting point of 43 and a clearing point of 48;

p-n-heptyloxybenzoic acid p'-isocyanophenyl ester having a melting point of 620 and a clearing point of 79; p-n-pentyicarbonyloxybenzoic acid p'-isocyanophenyi ester having a melting point of 555 and a clearing point of 86;

p-n-hexylcarbonyloxybenzoic acid p'-isocyanophenyl ester having a melting point of 757 and a clearing point of 85;

p-n-outyloxycarbonyloxybenzoic acid pisocyanophenyl ester having a melting point of 72 and a clearing point of 84;

p-n-hexyloxycarbonyloxybenzoic acid pisocyanophenyl ester having a melting point of 6060.5 and a clearing point of 755.

EXAMPLE 2 Preparation of p-n-heptylbenzoic acid p-isocyanophenyl ester 6.1 G. of p-n-heptylbenzoic acid p-formamidophenyl ester prepared in accordance with the procedure of Example 1 were dissolved in 40 ml. of dimethylformamide and cooled to 55. Then, 2.25 g. of thionyl chloride in 5 m1. of dimethylformamide were added dropwise. The resulting mixture was stirred for a few more minutes at the same temperature and then allowd to rise to 45. At this point, 4 g. of anhydrous soda were added. This mixture was again cooled below 50 and then stirred overnight at room temperature, whereupon the reaction mixture was poured over water and extracted with methylene chloride, and there was finally obtained a mixture of the starting material and of p-n-heptylbenzoic acid p'-isocyanophenyl ester. The p-n-heptylbenzoic acid can be isolated by chromatography on silica gel. Melting point 37.5-38, clearing point 50.55l.

EXAMPLE 3 Preparation of p-n-isocyanobenzoic acid p-hexyloxyphenyl ester 2.2 G. of p-formamidobenzoic acid p'-hexyloxyphenyl ester was dissolved in 100 ml. of methylene chloride and 25 ml. of triethylamine with warming at 40. With 15 stirring, 0.9 g. of phosgene in ml. of methylene chloride was added thereto. After an additional 2 hours at the mixture was treated with water and the methylene chloride phase washed with dilute hydrochloric acid and water, dried and concentrated. From 3.2 g. of the resulting product, there was obtained, after chromatography on silica gel with benzene/acetone and recrystallization from hexane, pure p-n-isocyanobenzoic acid p'-hexyloxyphenyl ester having a melting point of 8515 and a clearing point of 89.5.

The starting material p-forrnamidobenzoic acid phexyloxyphenyl ester was prepared as follows:

1.6 G. of p-aminobenzoic acid p-n-hexyloxyphenyl ester were treated in 75 ml. of toluene with 5 ml. of formic acid (100%) and boiled for 3 hours. The toluene and the formic acid are removed by distillation and, after recrystallization from ethyl acetate, there was obtained 1.7 g. of p-formamidobenzoic acid p-n-hexyloxyphenyl ester having a melting point of 189.5".

In a manner similar to that described above, the following compounds were prepared;

p-isocyanobenzoic acid p-n-hexylphenyl ester having a clearing point of 58and a melting point of p-isocyanobenzoic acid p-n-octylphenyl ester having a clearing point of 63.5 and a melting point of p-isocyanobenzoic acid pn-heptylcarbonyloxyphenyl ester having a clearing point of 99.5 and a melting point of 74. p-isocyanobenzoic acid p'-n-hexyloxycarbonyloxyphenyl ester having a clearing point of 95 and a melting point of 82.583.5 We claim:

1. A compound of the formula wherein X is and R is straight-chain alkyl of 1 to 7 carbon atoms, straight-chain alkoxy of 1 to 7 carbon atoms, straightchain alkanoyloxy of 1 to 7 carbon atoms or B-alkyloxycarbonyloxy wherein the alkoxy group is straightchain alkoxy of l to 7 carbon atoms.

2. In accordance with claim 1, a compound of the formula wherein R is straight-chain alkyl of 1 to 7 carbon atoms, straight-chain alkoxy of l to 7 carbon atoms, straight-chain alkanoyloxy of l to 7 carbon atoms or alkyloxycarbonyloxy wherein the alkoxy group is straight-chain alkoxy of l to 7 carbon atoms.

5. In accordance with claim 2, p-n-butylbenzoic acid p'-isocyanophenyl ester.

6. In accordance with claim 2, p-n-pentylbenzoic acid p-isocyanophenyl ester.

7. In accordance with claim 2, p-n-hexylbenzoic acid p-isocyanophenyl ester.

8. In accordance with claim 2, p-n-heptylbenzoic acid p-isocyanophenyl ester.

9. In accordance with claim 2, p-n-octylbenzoic acid p'-isocyanophenyl ester.

10. In accordance with claim 2, p-n-heptyloxybenzoic acid p'-isocyanophenyl ester.

11. In accordance with claim 2, p-n-pentylcarbonyloxybenzoic acid p-isocyanophenyl ester.

12. In accordance with claim 2, p-n-hexylcarbonyloxybenzoic acid p-isocyanophenyl ester.

13. In accordance with claim 2, p-n-heptylcarbonyloxybenzoic acid p'-isocyanophenyl ester.

14. In accordance with claim 2, p-n-butyloxycarbonyloxybenzoic acid p-isocyanophenyl ester.

15. In accordance with claim 2, p-n-hexyloxycarbonyloxybenzoic acid p'-isocyanophenyl ester.

16. In accordance with claim 3, p-isocyanobenzoic acid p-n-hexylphenyl ester.

17. In accordance with claim 3, p-isocyanobenzoic acid p-n-hexyloxyphenyl ester.

18. In accordance with claim 3, p-isocyanobenzoic acid p-n-octylphenyl ester.

19. In accordance with claim 3, p-isocyanobenzoic acid p-n-heptylcarbonyloxyphenyl ester.

20. In accordance with claim 3, p-isocyanobenzoic acid p'-n-hexyloxycarbonyloxyphenyl ester.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. I 3,925,444

DATED 1 December 9, 1975 INVENTOWS) 3 Arthur Boller & Hanspeter Scherrer It is certified that error appears in the above-identified patent and that sard Letters Patent are hereby corrected as shown below:

Column 12, claim 1, line 65, "Balky10X should be:

alkylox- Column 13, claim 2 line 7,"carobn" should be:

carbon Column 13, claim 2, line 10, "B-alkyloxycarbonyloxy" should be:

alkylo xyc arbonyloxy Signed and Sealed this eleventh Of May1976 [SEAL] ,4 rresr:

RUTH C MASON C. MARSHALL DANN lIIx'XIIHX ()H u'e' ('mnmissinm'r vj'luu'uls and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF (IORRECTION PATENT NO. 3,925,444

DATED December 9, 1975 INVENTO RKS) Arthur Boller & Hanspeter Scherrer It is certified that error appears in the aboveiderrtrtied patent and that sard Letters Patent are hereby corrected as shown below:

Column 12, claim 1, line 65, "5-alkylox" should be:

alkylox- Column 13, claim 2, line 7,"carobn" should be:

carbon Column 13, claim 2, line 10, "8-alkyloxycarbonyloxy" should be:

alkylo Xyc arbonyloxy Signed and Bicalcd this eleventh Day of May1976 [SEAL] AIICSK RUTH C. MASON C. MARSHALL DANN .IIH I IX Uflll' ('ummisxr'unur uj'luu'nls and Trademarks 

1. A COMPOUND OF THE FORMULA
 2. In accordance with claim 1, a compound of the formula
 3. (amended) A compound in accordance with claim 2, wherein R is straight-chain alkyl of 1 to 7 carbon atoms.
 4. (amended) In accordance with claim 1, a compound of the formula
 5. In accordance with claim 2, p-n-butylbenzoic acid p''-isocyanophenyl ester.
 6. In accordance with claim 2, p-n-pentylbenzoic acid p''-isocyanophenyl ester.
 7. In accordance with claim 2, p-n-hexylbenzoic acid p''-isocyanophenyl ester.
 8. In accordance with claim 2, p-n-heptylbenzoic acid p''-isocyanophenyl ester.
 9. In accordance with claim 2, p-n-octylbenzoic acid p''-isocyanophenyl ester.
 10. In accordance with claim 2, p-n-heptyloxybenzoic acid p''-isocyanophenyl ester.
 11. In accordance with claim 2, p-n-pentylcarbonyloxybenzoic acid p''-isocyanophenyl ester.
 12. In accordance with claim 2, p-n-hexylcarbonyloxybenzoic acid p''-isocyanophenyl ester.
 13. In accordance with claim 2, p-n-heptylcarbonyloxybenzoic acid p''-isocyanophenyl ester.
 14. In accordance with claim 2, p-n-butyloxycarbonyloxybenzoic acid p''-isocyanophenyl ester.
 15. In accordance with claim 2, p-n-hexyloxycarbonyloxybenzoic acid p''-isocyanophenyl ester.
 16. In accordance with claim 3, p-isocyanobenzoic acid p''-n-hexylphenyl ester.
 17. In accordance with claim 3, p-isocyanobenzoic acid p''-n-hexyloxyphenyl ester.
 18. In accordance with claim 3, p-isocyanobenzoic acid p''-n-octylphenyl ester.
 19. In accordance with claim 3, p-isocyanobenzoic acid p''-n-heptylcarbonyloxyphenyl ester.
 20. In accordance with claim 3, p-isocyanobenzoic acid p''-n-hexyloxycarbonyloxyphenyl ester. 